Reducing Agent
A reducing agent (reductant) is a substance that donates electrons to another species in a redox reaction, causing that species to be reduced while the reducing agent itself is oxidized. Strong reducing agents include hydrogen gas (H₂), carbon (C), metals such as sodium and iron, and compounds like sodium borohydride (NaBH₄). Reducing agents are essential in metallurgy for extracting metals from ores, in organic synthesis, and in biological processes such as the Calvin cycle.
Common Reducing Agents and Their Applications
| Reducing Agent | Formula | Oxidized Product | Application |
|---|---|---|---|
| Hydrogen gas | H₂ | H⁺ or H₂O | Hydrogenation of fats, fuel cells |
| Carbon (coke) | C | CO or CO₂ | Iron smelting in blast furnace |
| Sodium | Na | Na⁺ | Chemical synthesis, sodium lamps |
| Iron | Fe | Fe²⁺ or Fe³⁺ | Cementation of copper, corrosion |
| Sodium borohydride | NaBH₄ | B(OH)₄⁻ | Reduction of aldehydes/ketones |
| Hydrogen sulfide | H₂S | S or SO₄²⁻ | Analytical chemistry, industrial |
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Related Terms
Oxidizing Agent
An oxidizing agent (oxidant) is a substance that accepts electrons from another species during a redox reaction, thereby causing that other species to be oxidized while the oxidizing agent itself is reduced. Common oxidizing agents include oxygen (O₂), hydrogen peroxide (H₂O₂), potassium permanganate (KMnO₄), and chlorine (Cl₂). Oxidizing agents are critical in combustion, corrosion, bleaching, respiration, and industrial synthesis processes.
Oxidation Number
The oxidation number (or oxidation state) is a hypothetical charge assigned to an atom in a molecule or ion, assuming all bonds are fully ionic and electrons are transferred to the more electronegative atom. It is a bookkeeping tool used to track electron transfer in redox reactions, with defined rules for elements, ions, and compounds. Oxidation numbers help identify which species is oxidized (loses electrons, oxidation number increases) and which is reduced (gains electrons, oxidation number decreases) in a reaction.
From Latin "reducere" (to lead back, to restore) and "agens" (doing, acting). The term reflects the historical idea of restoring a metal from its oxide — "reduction" originally meant removing oxygen from a compound, coined in the context of metallurgy and later generalized to electron donation.